I believe there is a law that mailboxes have to be able to be run over..
to limit personal injury ..
If you have proof call the post office and complain to them also ..
A Guide to USPS Mailbox Regulations | MailBoss
General USPS Requirements for Curbside Residential Mailboxes
All manufactured mailboxes must meet the internal and external dimension requirements of the USPS.
Curbside mailboxes must be placed on the right-hand side of the road and facing outward so that mail carriers can access it easily without leaving their vehicle.
The box or house number on a mailbox must be represented in numbers that are at least 1 inch tall, and they must be positioned on the front or flag side of the box.
Mailboxes must be placed 6 to 8 inches away from the curb; the slot or door must be 41 to 45 inches from the ground.
Curbside mailbox posts should be buried less than 24 inches deep and made from wood no larger than 4 inches high by 4 inches wide. Steel or aluminum pipes with a 2-inch diameter are also acceptable.
Newspaper receptacles may be mounted on the same post as the mailbox, but they must not contact it directly or be supported by it.
Edit -- Some states/cities also mandate Break Away Poles on certain roads and highways ..